Copper extraction process



Jah. 19, 1932 w. E. GREENAWALT 1,841,437

COPPER EXTRCTION PROCESS Filed Nov. 9, 1926 ORB ) Crusher CaLOHLCa e..

Classlflcr Amd. Sol ution Acxd. Soluiwn f Pul p an d. Cu 5g* e. S'ng W t H 5 .A a3 C Soluhon 0:. Bccluccr CaOH)L CUS Preclpll'a1'5e .Low Grad: Conc. .y 501.

Roasimg Tdllmg Roashng FUTTIHCC High Grade Con c. Be sdue FU fnace- H1 9h Grad Coppcrolxlde Amd USO4 Solu. lon

l-oul Copper Solu onMcId) x A n Anodss 50 Amd Re cer Patented Jan. 19; 1932 if e e, uNirEnjSTATES;-

YY y i WILLIAM kApplication inegi'inventer 9,1926; ""serilino. 147,9;24,

j rlhe'process has as'its: object the production of electrolytic copper. from its oresfwit'hout resorting-to regular lsmelting and refining methods, which, in most-mining distriets,are` Y j too expensive for general adoptionfespecially in small or. medium sized units.;

' Thefollovving considerations are thelprin-V cipallfactors governing the process, andfWhen these are understood the process Cani beveasily i comprehended.

The two outstanding di'icultiesvin "the treatment of high grade copper. ore yor concentrate by leaching andfelectrolysisgare,A first: theormation of'ferrites andferrates i in roastingfwhich results in high taili'ng loss on leaching, Yand second: thev solubility of' iron and other impurities,` which; are lalways dissolved 'with the copper and Which cause trouble 'inleaohing and vinv the electrolytic deposition of the copper '-rom :the impune These "diiculties can.` be

copper solutions. Y l y minimized, but it isthought that. the present process presents advantages in this direction,'foverf-the usualmethods. 25 l Most mines,y or Amining'd'stricts-produce largey amounts of .,lowFfgrade: copperyore, usually inthe :form of. sulphide, the sulphide and oxide (includingcarbonateand silicate) mixed.` L Ineither. case/theI general.

3'@ method ofV procedure*v is to' separate ythe sul'- phidemineral from vthe ganguejto'form a concentrate.` .This concentrate isfusually fof" relatively lowgrade, as 4compared with the theoretical percentage 'of copper inthejmin Y eralogi'cal combinationof `:the: copper 1minerals. Considerable gangue klis' vassociated AVWith the copper inthe concentrate, fand usually a large: amount oifiron,either4 asflpy-y rites, or combined mineralogically with the 40 `copper-Fas in bornite or"olialcopfyrite. Quite `frequently chalcocite, having thermineralogicalv formula of Gu2S,-Will form aconstituent of the various copperlores, and to someeX't-ent *A also ycovellite, whichhasthe mineralogical "4'5 formula of CnS.H- z

c .In the; concentration treatment of ooppeif ores, the concentrate is usuallvso ,contamif nated With` iron, silica,y alumina-- etc.,y Vthat vigorous lluXing'is required for good` smelting conditions, and this :makes a smelting Voen'tratelWill contain.a.relativelyirlarge:porL vtion off the totalwcopperff VUsually thisrelaf Y K eratredlrinto'v: i

indicated, fif;y much of thecopperljin the ore t inthe; form otk chalcooite or bor-nite, ,and

process' expensive to install and expensive to operate@ Where `povfver is cheapi andfuel is `costly, electric smeltingwouldappearto oer required, yhas led to failure or'disappointment 'Whereverit hasbeen-tri'edrg;

n -In the concentrationtreatment-of mine ore, eitherl fbyxjgravity or otation, a. )Certain I amount'of `very high gradejconcentrate'may be separatedfrom the large' amount: ofthe ordinary sulphide: concentrate, b ut thefrela v tivelyrsmall amount overy highgradeecontively fsniallf portionofli'high'igradeconoenr trateiwill" be zintheform` of' chez-*practically pure-,miner'als-ehalcocite, bor'nite; andchalf J0 oopyrite. `Pure lchalcolcite@contains 798% copperfand20-2 sulphu'gpure bornite conL tainsy 155.8% copper5i1286% sulphur,` and V16.36% -iron;1. pure 'chaloopyriteglcontains Or 30 pounds,ofjcopperIper;ton,lorjcontain#V Y the 'ratio offconcentration is 10- fin'toL Wey Y .wouldihav`e, as theresult olfy the concentration Y* f Y y a9071wns minet 0.25% ciippr f uns);

`l0 #011s ,CDCeflltltei' 127.5%V Coppel: (255 lbs?) a jpaoglbuspftqtng L' i j' 1.

Ther` tentons" ofy ooncentrate 4may beisepaf c 1.5 uns tigt 'geen ertegen@ m/f i 'stef'. Y'c (110001105.),150mmtoen.A ,8p-5 *2011s V10W stede Corietiete 462% undermost `'conditions to get ,21,50% c9ppelr concntreten. the relatwelyLSlrmfflllL amounts l' iespeciallyfwhen the. water this is usually the case in what are known as porphyry, or disseminated, deposits. It will be understood, however, that the process is not particularly limited to the percentage of copper in the high grade concentrate, but that the higher the grade of the high grade concentrate, the better the'process can be oper ated asa whole- Having made the separation of the mineral from the gangue and divided the mineral into Y a relatively small amount of high-grade con! centrate and a relatively large amount of low grade concentrate, the method Vof procedure is as follows, reference may be made to the accompanying drawing which is a iow sheet. of the process, in diagrammatic'plan.

The relatively small amount of high` grade concentrate, which according to the specific case. assumed for Villustration purposes will consist of 1.5 ton-s of lCoppel' COIlCeIl'JIce per 100tonsl of original ore, is roasted so as to make as much-as practical of the copper water soluble and a highpercentage solubleV in dilutel acid. VBy careful roasting froml 80%.150 85 of--the copper can bemade soluble in waterand fro-1n 85% to 97% soluble in dfil-"ute acid; c L

When copper ore or concentrate is'roasted so` as toA .makeza large portion of the copper wacersoluble, some iron is also made soluble,

but the amount of water soluble iron is small i hatched with water or very vdilute acid,.-wh ich :will extract `from 80% to 8'5 of the copper,

' 4and :thewresulting copper sulphate; solution willbe quite pure, altho it will contain small amountsof iron and other imp.urities,.butnot in sufficient' amounts tov vseriously affect the subsequent 'electro` Adeposition of the copper.

The copper solution flows from.` theleaching tank No. 1 into ther settlerNo. 1. This settler'may also act asa storage tank. may also'` act as a reducer for ferrie iron', when the solution isi-treated with coppersulphide. High grade copper sulphidefor this purpose be obtainedffrom the originaljore, by fusion, lor as GuS precipitate obtained in sulphide. v y The copper solutionilows into the 'copper tanks No. 1, wherethecopper is deposited as electrolytic copper of ygreat purity, with'the treating lean and foul solution with hydrogen simultaneous regeneration of acid. @wing to thesmall 'amount of injurious impurities in the electrolyte, thesolutioncanv be fairly im# vics concentrate leaching and electrolytic circuit. A portion of it may be returned to the roasted high grade concentrate leaching tank No. 1. If the solution issues from the leaching tank N o. 1, containing, say 8% o r 10% copper, and containing only a small amount of iron, it is quite` practical` to improverish the solution downY toabout. 2% copper, with a very high ampere eliciency. It is preferred to deposit most of the copper in the copper tanks No. l, from a rich copper solution, which will result in the best possible copper and the-higl'iest ampere efficiency obtainable under the conditions, and then pass the impoverished solution t-o copper tanks No. 2, where the copper may be reduced.V to the desired extent, say, to 1% or less. This solutionjlow in copper and high in acid is then passed tothe low grade concentrate leaching and velcctrolytic circuit.

The relatively large amount of low grade concentrate, which'according to the specic case l' assumed for illustration purposes will consist of 8.5 tons of 6.2% copper concentrate,

per tons of original ore, is roasted so as to Vmake as much; copperv water soluble as practical, an-d a highpercentage soluble in dilute acid.V From7'5% to 85% of the copper can be made .waterY soluble by careful roasting, and from 85% to V97% can. be. rna'd'e acid soluble.

It is preferred to add the leached tailing i from the high grade concentrate to the low grade concentrate,l and roast the mixture. This means a double roasting for the high grade concentrate, but sincel the amount of high grade'concentrate residue is very small and'will usually contain copper worthirecovering, this method o f procedure olfers evident advantages. The residue will beonly a half or athirdof theA original. highgrade concenn trate. .The extraction by double-*roastingfof the high grade concentrate, can'bemade 'almost complete, or atleast givega`Y final residue aslow, in copper as the` residue resulting from leaching the roasted lowpgrade' concentrate.

The extraction? may be as-'hi-gh as 97 %I to 99% i vWater soluble copper solntionthan desired.,

the solution may be treated .with highgrade g copper oxide, obtained from :roasting high grade concentrate; Thev water-soluble cop per solution is transferred to the high grade concentrate leaching and electrolytic circuit,

prefer-ably by using f it.' as. the. leach .water so- L lutionri'or the roasted high-grade', concentrate( Thi'swill give'a very i'i'chfa'nd alquite pure neutral: copper sulphatesolutiomand the' amount loi'fvvater usedWill be'reduced tol a minimum. y With care in leaching/a large portion of theironpmayhe precipitated from theA Water soluble copper 'solution :with the f high grade roasted concentrate, 'and when the' 7 residueis roasted, the precipitated iron will be' made insoluble. The Water soluble ,copper solut'oii-obtainedby first leaching the roasted lovv grade concentrate and then the roast'` ed high grade concentrate, is thenV electrolyzed to 4deposit the copper. andl regenerate acid,`as described for the copper'- sulphate solution obtained by `Water leaching-'the high grade concentrate. ACoppersulphate is quite soluble in Water'. 'At 70deg.' C., Whichwould be a fair temperature oi the Water in leach# ing hot-roasted concentrate, a -Water saturatedlsolution of coppersulphatewill contain 12.93%1copper, and thereshouldbehno diiiiculty 'in keeping the head solutionfor` copperdeposition at'from8% to 10% copper, in' leaching. the roasted -conceiitrate` 'as `de'- scribed."l Such a rich"copperfsolution` isnot necessary, nor. may Vit be desired,F but it 'is The Yregenerated l acid solution, resulting from the deposition' ofthecopper from the l relatively pure Wat-er 'soluble copper solution, is quite free fromA ingurious impurities. portion of this acid solution may be added to the Watenff'or the Water" soluble 'copper Jsolution in'lainount sothatther'acid Will be quickly neutralized by the copper; in the roasted concentrate, Awhich Vis insoluble Water.' This coppenwill be mostly in the orin ofroxide; Iron is'not readily soluble in a ivealr acid solu- 'tion`,but, at'the saine time; the copper'oxide 4-in-ff'the roasted concentrateA Will vbemgluiclil-yVv f dissolved in a Weaki acid solution.' It is `'pracf tical, therefore, to leachout the larger"pjortion of the-readily solubleloxidefof copper with a very Weak acid solution, Without appreciably increasing thjeironcontent of the solution, and, as already indicated, i'flthe iron occursin the solutionin -undesirable amounts,

-it can easily be' precipitated Jfrom the neutral solution With an excess of concentrated copi per oxide.v The precipitated iron in the high gradeV concentratefresidue can be made insoluble 'by 'roasting-'the `residue With the loul l gradeconcentrate. "It should `beV practical,

in this `Way,"toextract- 80% ofthe 'copper lfreinthe@roastedulovv grade concentrate and '95% ofthe copper from thero'astedjhgh ygrade concentrate, Without appreciably foulingthe solution. I

"If the extracti'onoflthe' copper Vfrom the roasted high grade concentratei's95'%`, and-` thejloss of Weight-by roasting and leaching is 60%, "the hig'l'i grade'. concentrated y leached residue Will still contain about 6.25% copper. lMuch .off this copper' in the residue f can be ing'of the roastedliigh grade concentrateinay beY dispensedy Withf^` and :the residueL obtained centrate. and roastedwith' it.4 NVith the" ree` Vgradey concentrate and theV cycle repeated orefcontans copper in oxidized form, such as extracted :with strongk acid, andthe resulting` highly impure solution" transferred Vto Ethe lovvgrade concentrategleachingf`ande1ectro- ,i i

lytic/circuit, but ordinarilyjghis, extra leachi' fromv leachingl-wvithwater or've'iy rdilute'acid solution'sniay be added to the low gradecon-f roasting fandre-leachiiigof this highA grade leach concentrate residue the extraction Will bealmostcomplete, f 1- f f. iWashWater, or lean Water soluble copper solution,I resulting fromAVI 1 leaching yof one charge of either the roasted- 'high' .gradeY orv loivgrade concentrate, may e used as the head solution foranotherlcharge 'f It will be noticedithat, Water lleaching, loi" very dilute acid leaching,so as to obtain neu# Y tral, .or practicallyf neutral solutions, an

amount oflivater, *or regenerated acide'soluj A tion, is discarded,ffequal"tothe amount-Lof- Water-f added, and that inr` this-' Way the Sinju'v rious impurities in' the rich,` orfwaterv soluble" the regenerated solution obtainedl from f depositing the copperV romfthefvvater 'soluble copper 'solutionfr This/strong acid solution Willbe usually quiteimp'uregk It Willicontan p the relatively smallamountof impurity from `iilo f thevvater soluble copper'leaching and elec- Y trolytic circuit, and the Arelatively large 'Y amount` of rvimpurity resulting from `leacl'iing j s the roasted 10W grade concentrate vWithgthe relatively lstrong acid solution. ;The strong "T05 acid solution will dissolve the ycopperfin the roastedlovv grade concentrate rwhich was not soluble in Water, or very-dilutevacid, if l i thetotal extraction `is 95% the leached roasted low grade residue-WillI contain`- about original concentrate.

The impure solution, 'containing salts of iron and other impurities, flows into :the set# tler, or reducer No; 2, Where it maybeclari viedand treatedwith copper sulphide to reduce'ferric iron' to ferrous'iron. The'solul tion then `flows into the SO2 reducer, and

fronithe reducerfinto the storage tanlnand .a

:troml the s toragetank into the copper tanks No; 8, Where the copper isy depositedfand acid andferric iron regenerated. A portion of the solution is returned to the roasted low until thecopper VVin the roasted low gradek concentrate is zsuliicientlyextracted, vas de,- scribed ,morejiin detail infmy :Patent No. 1,483,056, Feb. 5, 1924,'and` anothenportion,

th'efexcess, may bervvaste'dor, ifftheoriginal y ilor '70.31% coppenfbased cnfthe Weight of the,k f

@iis

fisc

.49 at least in part,by Washing the oversize with thev oxide, carbonate, orsilicate`,'the excess may be used to leachthe `oxidized copper from the original ore, or from'the conceitV trator tailing, preferably as willnowfbe described.vr Y e y w The ore,'which may bepresuined to be crushed to about l/Jr. inch in the primary crusher, is fed into theY rod mill, where it is grinding, since that will require the least amount of water and have the least amount of returned oversize, and consequently a small circulating load,and this oversize can be kept fairly low, even-as low as 25% and lower, without appreciably' reducing the eiiiciencyot the rod mill. Y

Whenthe nnely ground ore pulp, containing, say, about 25% water, issues from the rod mill, it is mixed with about three times the amount of acid solution produced by leaching andelectrolysis `in the treatment of the concentrate as described. This will give about the right proportion of liquid to solids for the classification to 48 mesh. This acid pulp then flows into the classifier where the acid solution acts upon thel oxidized copper in theore to dissolve it, while at the sameV time a classification is made to i8 mesh. The minus 48 mesh passes to the copper solution separatom'a-nd the oversize is returned tothe rod mill for re-grinding.

In order to avoid injurious effects o' acid and soluble copper in the rod mill, the' oversize is `washed to free it from acid and soluble copper, and thisr can be conveniently done7 a slightly alkaline solution and containing a precipitant for the small amount of' copper in the washed oversize. .This step is easily and cheaply carried out,` and with the exceptio-n oi this step, the grinding-and classiiication is about the same as grinding and' classification with ordinary water. The precipitated copper from washing the oversize inv regrinding is re-dissolved 'inthe classifier.

e The operation of grinding the ore and its classification and leaching in an acid solution can be made clear by' assuming a specic case. Suppose the grinding in the rod .mill is done so that there will be ai return of 25% oversize.v This will not greatl reduce theefiiciency of the rod mill from its maximum, and the extra cost of grinding, as compared with a normal oversize return of 'from40% to 50%, will be nominal. With a 25% oversize return, there would be 500 pounds of oversize porton of ore fed to the rod mill. The water or dilute acid solution of this oversize in the upper portion of the classifier, would'be about 20%, or 100 pounds of solution, for the .500' pounds of oversize,

or about 1.3 pounds of acid and 1.3 pounds of copper, per ton of ore groundto the desired fineness to pass the classiiier, assuming the acid content of the solution in the classifier after treating the oreat 1.0%, and the copper content rat 1.0%.- 1.3 pounds of acid would therefore have to be neutralized and 1.3 pounds of copper would have to be precipitated,'per ton of ground ore, assuming that the oversize is not washed atall. If, however, the oversize is water Washed in the upper portion ofthe classifier, so as to displace acid solution with water, most of the acid and mostv of the copper can be washed from the oversize, depending on the amount ot the washing. The washing can be Ina-de practically complete, but this might add too much water to the classilier and thus undesirably dilute the acid solution. Butl if only about enough water is added to the upper portion of the classifier to displace most of the acid and copper in the oversize, no appreciable amount of Water will be addedto the acid solution in the classifier'. The acid and the copper in the oversize, as it is discharged from the classifier into the washer, may bereduced to about 25%, or about 0.25gpound to 0.5 pound of acid and of copper, per ton of ore ground. This amount of acid is easily neutralized and this amount of copper is easily precipitated in the washer, by washing with a dilute alkaline solution containing a precipitant for the copper'. A small amount of' flotation agent maybe added to the washer to overiow a portion of the precipitated copper in the washer, into the classifier. -The small amount of acid can also be quickly neutralized by mixing the oversize with new ore to be ground, soY that the process is not a delicate one, and can be carried out at ai very nominal extra expense over ordinary wet grinding, and much cheaper than dry grindf to the same fineness.

.Y It is nrefer'redt'o separate the richer portion of thecopper solution from the ore pulp, in the copper solutionseparator, but without attempting to separate all of the soluble copper .from the pulp, by excessive washing. The richer impure copper solution, without filteringor unnecessary clarication. is treated a precipitan-t for the copper, preferably with hydrogen sulphide, by means of which the copper is precipitated as copper sulphide with a regeneration of an equivalent of acid. The mixture of solution and precipitate iiows into the CuSseparator, where the CnSI is separated from the acid solution. The CuS may be added tio the high gra-de concentrate and roasted, or a portion, o-r all of it, may be used as a reducing agent forfer'ric iron produced 'in the deposition ofthe copper. The barren' acid' solution may be wasted, or a portionof it may be returned to the classifier for reuse.

Since the larger portion of the copper both zthe roasted highy grade and loWf grade concentrate `is soluble 'in Water, andsince an equivalentl ofacid isregenerated from the water soluble copper, as Well'as a vcertain amountiroin the acid soluble copper, ythe copper in the original ore, inthe. forinxof oxide, can be lea-ehedfout yWithout any acid expense.

roastedconcentrate is Water soluble, or'about 204i() poundsofthe total 2550 pounds inthe concentrate, abundance of acid will ordinarilyberegenerated to dissolve, say, 70% of the assumed 0.25%,.,of the oxidized copper'in the originaly ore, or about 3l() pounds.;Y That is toV say, 'thereWill be about seven times as much acid. regenerated in depositing about 2550 pounds of copperobtained from the concentrate, as that theoretically required todist solve `the 310 pounds of copper, in oxidized precipitate the copper. .If the Solution is to be made neutralor slightly alkaline, a small lamount of caustic. limey or caustic sodarmay be added to theleac'hed ore, as it goes into the concentrator, Where the sulphidecopper concentrate is separated from thegangue, either by gravity or lotation or byboth combined.

The CnS precipitatefwill be floated With the otherY sulphidesY inthe ore fand 'formi part of the high grade concentrate; The tailing may be wasted."f= i' In ele'ctrolyzing i the rich vvater soluble copper 'selutior'i'as described,V a fairlyhigh acid solution Will beregenerated,andyasthis high acid solution linayf advantageouslyvbe dilute'dffi-'or leaching the `oxidized 'cop-per, it canl conveniently 'and profitably be done lby grindingtlieore vWet and simply 'addingthef acid solution to theewet ground orefto'give the: pulp the consistency for the f desired ic'lassiiicatioiif Y In niostmixed ores, that is to say,"` ores containing the copper both -as-the oxideand the; v sulphide,` the--sulpliide" is frequently coated with zin-oxidized '.(usually carbonate) film.; f The oxidein the ore isusually the result of the oxidation ofthe sulphide, and while much oi the oxide (including carbonate) coating may be removed by grinding, nevertheless, it cannot be so perfectlyremovedfas'not to vpresent a seriousdi'mculty in many, or inost cases forltlie bestconditions for flotation; If,

on the other hand, the oxidizedportion' of thel copper in the ore -isfirstremoved bya solvent process, the sulphide KipperA isV yfully/ge,xposed .andthe best conditiensare obtainedfor'isiicfY cessfulgflotation,l Withthe consequent hig'h'y l i j estf total,V extraction ioffthe; copper,` both-in f' its oxide and sulphide combinations. Leach 70y .advantages over, leachinglfafter flotation,l

ing before Yflotationl presents certain decided Y iQ traction of the copper.,- and the process, asa Whole, is greatly simplified.l 1.,. f,

Where leaching precedes flotation, con# stitiites thet entire p'rocess,the forefis prac# tically alwaysv crushed dry. Dry; grinding, f j

with the accompanying screening, -ispexpensive and, quite ,a nuisance Y'if .the grinding is tine forfotation Finedry grindingofV low grade ,copper oresvis rarely, :if ever, attempted for leaching only.

,e Vet grinding is `much to be preferred, be-` cause itis cheaper than dry grinding, andthe screening and dustjnuisances are,v avoided. The diiculty -intWet grinding; and subsequent leachingghowever, arisesthat the Water nec-` essary forpfwet grinding and ,classication has v` l to be` eliminatedjto vavoid"inidue ,dilution-y `and, Waste of the solventpand it iscquite imfggf practical to dewaterthe orepulp muchbelow Without ltering, andiiilteringis tooextion ylargequantities V`of Wash water have to be appliedto the acid leached `residues to recover the soluble copper.' Thelossofacid by thislexcessive -additioncof `Water, and theprecipitation ofthe copperfroni the large.

volumes'of Wash' Water .presenti ,serious Aeconoinic. problems.

Ordinarilythe cost ofjfacid re'f'giuiredfor Y .pensive in lthe treatmentgoflow grade ores. t Then, againinthe usual conditionsof opera; l

leaching `presents a .seriousproblem ,in yc'o'pf `per mining districts; 1` Inifsmall leachingv iii-- stallations an J ,acidplant AWould be toov ex-V f ypensive to installandto operate. vAcid could not ordinarily y be delivered in .any ordinary mining district ffor, less; thanabout $2`0ffpe`r t ten, andfeven iffinanufactured on the ground vvthe cost would.begaboiitldper tonlfpThisr los.. Y

acid costgisrafvoided'by thejpresentjproces's, l

" Vand the acid expense c for, leaching is-practically nothing. e Itis highly. desirable also `,that all VVof the copper should be obtainable' as theI electrolyticmetal,.`salable `direct Vto Vthe g y consumergtoavoidexcessive..transportation f and reiininggcharges.y

This, t/.OQgis "realized inthepresent process,l i t from leaching they original ore ean'be regu# lated solasfto obtain suiiicient copperforef-I 4 ective-.electrolytic deposition orprecipitaf faportionof theffolil solution i tion, it is `preferred-to precipitate ittli'at Way", t

as being easier ',andfcheaperfthen hydregen sulphide. precipitation. :It will usually ,be `quite practical to .get a suiciently richcop` persolutionjfrom ythe largetonnageofforigiy i ,naloretd make this step {advisableltfvvill Valso usually be desirable to reduce the copper @enriches Practical' inthe XQSS ,regenerated T130 high grade copper concentrate, the high wir A, With -the impure regenerated acidv solution 'from the copper tanks,-an'dthen electrolyzingth'emixedlsolution to impoverish or strip y it`-o 'copper to the desired extent', in the copperstripping tanlrs.V "llhislmayA be done et- "fectively by' applying sulphuidioxide from I the roasting'ilurnace to the -oulfcopper solutionlto -reduceferric'iron' to `the ferrouscondition, and then electrolyzing'the foul copper solution',lreducedin acid, to deposit the copper. In this Way, from; twoAv to three poundsof additional acidmay be regenerated, per pound of copper deposited from the 'foul 'sollit-ion.'V Tlie'niiXing'- ofthev solutions reduces' theacidity, and peri'nit's-ofmore ellective' reductionofthe "ferrie iron, and makes practic'a'l quite closestripping of the copper from they solution; The cathodesA from the foul solution copper:stripping'tanks-ivillusually be quite impure; Y Theyinaybe refined Vby using-` them as ysoluble anodes ini the practically pure copper solution inthe copper tanks No; 1. TheV cathodes `produced in copper tanks No. 1 and No. 2 Willbeof great purity, and the cathodes in'CoppertanksN'o. 3 can be made soby depositing fromA a solution which is nottoo lean in copper, and then stripping the copper in the copper stripping tanks;

, It the copper in'y the rich Jfoul solution obtained from ,leaching the original ore is dev :posited,electrolytically, the remaining` very 'lean solution may be treated' with hydrogen sulphide to precipitate the" copper as sul?- phide, and theburren'solution Wasted. rThe VWasted solutionwouldv about equal in amount the freshwater added for'vvater leaching the roasted concentrate', plus that necessary or desirable' to Wash' soluble copper Vfrom the ore,

Aprep'airatorlv kto flotation or 'gravity concentration.4 Y K, y

"l/Vhen the copper' concentrate permits of .separation intoa'high grade anda low grade concentrate, certainy advantages Will result bythe treatment described. v"lheiroast'ing of` copper concentrate to get a high extraction ofthe copper is by no means simple. It requires care, especially if a high ypercentage of thecopper is to be made Water soluble Without making a large amount of Water soluble iron. If the larger vportion of the copper can grade concentratecan he given the necessary care to get a high extraction oi the copper and apure 'electrolytic metal. By separating a small amount of highgrade concentrate, the

tion; As applied to the specific case for illustration, about 83% of the precious metals will go Withtheconcentrate and about 17% with the concentrator tailing; and ithe concentrate is divided into a high grade concentrate and a loW grade concentrate, of theV precious metals Will be with the1.5tons of 50% copper concentrate, and about 40% of the precious metals Will'be With the 8.5 tons oi 6.2% copperconcentrate. The' treatment of the copper concentrate leached residue to recover the preciousmeta-ls Will depend on l their value and on the extentto which the copper can be extracted fromy the roasted concentrate, previous to leaching for the precious'metals. It the residue can becyanided, that would probably bethe bestv treatment for the recovery of the precious metals, but the cyaniding of copper lea'chedl residue Will depend almost entirely on the copper extraction. There should not be any dilliculty in getting a` sufficiently high extraction of the copper in the low grade4 concentrate to make cyaniding ofY the residue practical, and with the-double roastingA and leaching of the high grade concentrate, all of the leached copper concentrate-residue should be made amenable to cyanid'ation,l if -the precious metal content is of sufficient va-lue to Warrant the treatment of. all the concentrate residue. If, however, the precious metal values are so small as not to .Warrant ageneraltreatinent for their recovery, the high grade concentrate can be treatedv alonepfor the recoveryk of the preciouslmetals. Of the v3,000 pounds of copper in the 100Ytons of original lore 1500 pounds, or half of the copper, will be in the Y1.5 tons of high grade concentrate, andconsequently alsoabout half of the precious metals. lf the high grade c0ncentrate,

Vthrough roasting` and leaching is reduced in rWeight by 60%, theleached 1.5 tons of roasted high, gradeconcentrate residue Will Weigh about 0.6ttons, and Will contain all of the precious metals originally in the'high grade concentrate. Even if the pr-ecious metal content in the original ore is very low, it

-Would still probably be highlyprofitable to trated in the high grade concentrate, the

'leached high-grade concentrate residue Av'vouldassay*about $8.33, which could be very i bleby'- hydrolysis,

die

'Water soluble coppersolution, iron, and if the ysmall ainount of terric iron low, or rniniinuni cost for 4lytic process,

- in iron,'but this iron can profitably practical, chlorination!cangalinost always be successfully employed. l w L Ii the roasted conc-entrate visQiirsttreated with Water orA With'a yery dilutefacid solution,` so that dissolvediron is precipitated 'iointhe solution, or soluble iron inade insoluthe Waterl soluble copper solution Vcan be niaintainedquite low in solu-rv ble iron, but the precipitatedor hydrolyzed 'iron in the leachedconcentrate Will be dissolved by leaching'with the dilute acid solution in Which the acid is' in eXcess,lto dissolve f the acid, soluble copper Sironi the'concentr'ate. The copper can be readily-deposited rointhe vvery?A loW in formed by theelectrolysis is effectively re-V duced, the re-solution ofthe deposited cop# yper can be closelycontrolled. yThis makes possible a' wide variation in currentjdensity or effectiveelectrolysis; Wherel the cost of electricity is largely'govern d by peak loads `the electrolysis can be carriedoutuatfaniaai- -inurn current density:y (during` the daywhen `'the load-'factor 1 a minimum current 'thepower plant preaches and-recedes from Ythe p calrload.

for other` uses is low, and at den sity `when the :load vron for kother purposes his will` make possible, in Vmany cases-,"a

deposition, and the power cost`,in any electrois of prime importance.' Y

On the other hand, the acid soluble copper 'will be accompanied by high soluble iron.v

The stronger acid, Willdissolrfethe acid solule' iron and also the iron precipitated'froin the YWater soluble copper solutionf,'and that hydrolyzed in the concentrate. VThe acid soluble copper solution Will therefore be high f :The regulation of the curre'iitdensity of vtor the 24 hoursperday accor *varying intensity,` and cyclicallyV7 H regulated y Acreto separate 'a-high-grade anda lowvgrade l copper concentrate,roasting the high grade concentrate; roasting the. low grade concenthe roasted low' grade' con i sumpti'on of power;'cxtianeousfto the copper deposition circuit, will Vberniore yoi' less ld'ependent on the absence otferric iron in Vthe electrolyte.: Ferricf ironff'dissolves Icopper more vor less proportional to itsfpresence in the electrolyte. Alowncurreiitdensity, Which recovered.' It vcyaniding -ot they copper'leached residueisfor any reason iin-v concentrate, leaching "concentrate'to eXtractap'ortionfo'the cop- :mixing the'leachedroasted:high grade" concentrate residue with thelow grade conandl'eachingj 10oY power for copper per,

- centrate,

becontrolled, in the Y o the ironmay vbereggeiierated'y electrolyzing'j rornleaching the high deposit the.l copper and regenerate acid, Jvand '11- leachingr the Aroasted low` grade'concentratc ding'to the conconsumption 'of y ,y power for other purposes is at its peak, would beiquestionable econoiny if the ferriciron in theelectrolyte islhigh,onaccount of the' reo so' erric iron is-'low or maintained reduced,the`

solution of the deposited copper but if the re-solution of thecopp'er is small and the-,loss n in eiiiciencyfwould notlbe appreciable. f As a practical illustration, acell krooin could be designed for aniaXiinuin current density ofr l5 amperes per square-toot;y During the peak could be dropped square foot, with to 'as equalization' of the vpower of yerycheappower, especially Water power,

Vwhere the: load can be vniaintained jpractical .2Llliours, would -inalre possible the acquisition i ly constant forf'the ull-2lhours at about tlie saine'v cost asagreatly y ing, much lesstp'ower for the full 24horas; y

Iclaiin: .u f -1 l. *Ag process roasting copper' concentrate?" he` roasted .high grade roasting'-the mixture, the roastedinixture to extractthecopper.

grade and a lowgrade concentrate,r roasting tliej'low grade concen-v trate, leaching the roasted high grade" concen- S0111- c c centrate With said ,acidsolution.V

treating 'copper ,3. 'A' process comprising,

Varying yload /deliv'er- Y, j

2. A process comprising, treating` copperl ore to separate a high copper concentrate,l roasting the high grade.

Vloadorvother.power uses ythe current density low as5 amperes per L proportionate "diinunition l comprising, treatijn,frv copper if A ore to separate ahighgradeandallow vgrade n thehigh grade z95 ore to separate a high grade'anda low grade copper. concentrate, 'roasting the high grade concentrate, leaching the roaste'dvhigh grade j Y concentrate to 'extract a portion of the copper, adding the leached Vj residue of the roasted centra-te, .roasting the gradeV` concentrate :to

With said regenerated acid solution. y

4. A process comprising',l treating copper trate, Y leaching high grade concentrateto the lowgradefcofnlow gradeconcentr'ate, v thelcopper solution" obtained-f` regenerate acid, leaching the loW grade cony Vcopper solution separately ly pure copper solution to solution.v

ing the roasted low grade concentrate, and

copper concentrate, roasting the high grade concentrate to make a portion of the copper Water soluble, roasting the loW grade concentrate to make a portion of the coppeiwater soluble,` leaching the roasted loi-.v grade concentrate to extract a portion ofthe copper, leaching the roasted high grade concentrate with the copper solution obtained from leaching the roasted low grade concentrate, electrolyzing the resulting relatively pure copper solution to deposit the copper and regenerate acid, applying the regenerated acid solution to the partly leached roasted low grade copper concentrate to extract more copper, and `electrolyzing the resulting relatively impure from the relativedeposit the copper.

6. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roasting the high grade concentrate to make a portion of the'copper Water soluble, roasting tlielow grade concentrate 4to malte a portion ofi-the copper Water soluble, leaching the roasted loW grade concentrate to extract a portionoi1 the copper, leaching the roasted high grade concentrate with the copper solution obtained from leaching the roasted'low grade concentrate, electrolyzing the resulting copper solution to deposit the copper and regenerate acid, and

Y applying the regenerated Yacid solution to Athe roasted lon7 grade concentrate to extract an other portion of the copper.

7. A process comprising, treating copper ore to separatea high grade anda low grade concentrate, roasting the high grade concentrate, roasting the low grade concentrate, leaching the high grade concentraterto extract the copper, electrolyzing the resulting copper solution todeposit the copper and centrate with the regenerated acid solution, electrolyzing the resulting copper solution to deposit the copper and regener-ate acid, and dissolving the copper in the ore in its oxide .combinations With the regenerated acid solution.

8. A process comprising, treating copper ore to separate a high grade and a low grade copper concentrate, roasting the high grade concentrate7 roasting the low grade concentrate, leaching the high grade concentrate to extract a portion of the copper, electrolyzing the resultingcopper solutionto depositthe copper and regenerate acid, returning a portion of the regenerated acid solution` to the roasted high grade concentrate, and leaching the roasted low grade concentrate with another portion yof the regenerated acid relatively pure v. copper solution to deposit'tlie copper and naturally occurring in its oxide combinations.

l0. A process comprising, roasting copper concentrate to make a portion of the copper Water soluble Vand a portionV acid soluble, leaching the concentrate to extract the Water soluble copper, electrolyzing the resulting Water soluble copper solution to deposit the cop per and'regenerate acid, then leaching the concentrate withV` the regenerated Vacid solution to extract the acid soluble copper, then in a separate electrolytic circuit alternately subliec'ting the resulting impure copper solution containing salts of iron to electrolysis and to the action of sulphur dioxide vto deposit the copper and regenerate acid. and then leaching copper ore YWith the resulting impure regenerated acid solution to extractthe copper naturally occurring in the lore in its oxide (includin carbonate and silicate)` combinations.

ll. process comprising, roasting copper concentrate to malte a portion-of the copper Water soluble vand a portion acid soluble, leaching the concentrate to extract the Water soluble copper, electrolyzing the resulting water soluble copper solution to deposit the copper and regenerate acid, then leaching the concentratewith the regenerated acid solution to extract the acid soluble copper, electrolyzing the resulting impure copper solution in a separate electrolytic circuit to deposit the copper and regenerate acid, leaching copper ore with the resulting impure regenerated acid solution toextract the copper 'therefrom in its oxide (including carbonate leaching the concentrate to extract the Water soluble copper, electrolyzing the resulting Water soluble copper solutionto deposit the copper'and regenerate acid, then leaching the concentrate with the regenerated acid solution'to extract the acid soluble copper, electrolyzing the resulting impure copper soluu tion in aseparate electrolytic circuit to dethereofto deposit thewcopper,and-regenerate acid Aand ferrie iron,` vandi returning the- Ire`` sultlin g acid solutionto the ore to extract more copper therefrom in its oxide com.bin'atimsA Q13. A'proce'ss oftreating lnixedoxide andi sulphide copper orecompris'ing, treatingl thefV y ore to separatel a sulphide concentrate, roast ing the sulphide copper concentrate to make a portion ofthe copperwvater' soluble uand another portion acid'"soluble, fleachingfthe roasted concentrate to' dissolve ;the Water'soll' uble copper, then leaching the' vroasted j con centrate to 'extract-fthe, acid 'soluble copper,

separately Y electrolyzing the Water soluble copper `solution and the acid soluble copper f solution to deposit the copper and regenerate acid, applying the regenerated-,acid"solutionj from eiectrolyzing the5 Water YsolubleV 1 copper solution to extract the acid soluble copper in the roasted concentrate',and 'applying the acid solutionfobtained from electrolyzing the acid soluble copper solution to the ore or concentrator tailing to dissolve the copper therefrom in its oxide combinations.A

14;. A process of treating mixed oxide and sulphide copper ore comprising, grinding the ore,adding a dilute acid solution to the finely ground ore to extract the copper therefrom in its oxide combinations,separating a portion of theV resulting copper solution from the leached ore, L'subjecting the leached ore tov flotation or gravity concentration to separate a sulphide copper concentrate, roasting c the` concentrate, leaching .the roasted con? Vcentrate to extract the copper, electrolyzing the resulting copper solution to deposit the copper and regenerate acid, mixing the regeneratedacid solution still containing some copper with the copper solution obtained from r leaching the finely ground ore and electrolyzing the resulting mixed solution to deposit copper and regenerate acid, and applying the resulting regenerated acid solution to the finely ground ore to extract the copper therefrom in its oxide combinations,and re peating the cycle.

15. A process comprising, treatingv copper ore containing precious metals to separatea high grade and a loW grade concentrate, roast.-

ing the high grade concentrate, leaching the;

roasted high grade concentrate to extract a portion of the copper, mixing thejcopper leached roasted high grade residue With the unroasted low grade concentrate, roasting the mixture, leaching the roasted mixture tov extract the copper, andjleaching the copper leached mixture residue to extract .the precious metals.

16. A process comprising, -treating copper ore containing precious cmetals to 4separate la* high grade k'anda lowgrade concentrate, 'sepax Y' rately roasting 4and vfleac'hing'- the'I high y'grade and the `low grade concentrate to lextract the .l

cqppe", and'tieatingtheopper.leached'hgh i.

due to'recover-15h@l.pre;` *c

grade concentrateres '-17-A* copperextractionprocess compris-1.A i' y ing-treating copperploreto separate! a.high'f y gradeV andal low grate concentrate, 'sep arately roasting the high? grade and' the lovv grade'Y concentrate, le'achingoneofthe-roastedy con-f f. centrates toextract 4a portion ofthe 'copper asa relativelypure and relatively rich copper l solutionfV then leaching# the roastedconcen-L trates to"extractf1the c remainingfcopper as relatively impure copper solution,precipitatl;

ingthe 'copper'ffromlthe relatively'jrich and f relatively pure copper solution in'one electro-` y lytic circuit, andy precipitating they copper another electrolytic circuit. f

"18. Aicopper extraction process -compri's- -k ing,A roastingcopper-concentrate to make ,a portion of `the-copperWater soluble and a vfrom the relatively impurecopper solution iny 1 portion acid'solub'le,"leaching the roasted concentrate to extract a portion of the'copper as a relatively'pure and relatively rich copper solution, then leaching the roasted concen'y Y trate 4to 1 extract the remaining copper asa relatively; impure `copper solution, precipitating thecopperl vfrom the 'relatively pure i andrela'tively 'rich copperssolutionv inr one` electrolytic v`g circuit,- and Lifprecipitating i the y copper jfrom the :relatively impure copper solutionfin another yelectrolytic circuit. 'i

:19,- '/X'processv comprising, treating copper ore to Aseparate a high gradeand a low grade?r `concentrate, separatelyroasting the high grade and Ifthe low. grade concentrate,,separatel-yleaching-'the roasted high grade and105 thev low grade concentrate?,and` electrolyzing they resulting V'copper solution tovgdep'osit the copper, rand transferringfthe'richer Afand purer portion y.of the 4co'pperI--solution from leaching the lowgrade lconcentrate'to the'high grade concentrate leachingand electrolytic circuitand transferring the leaner and foulerk portion of thecoppersolutipn'from leaching the high grade "concentratetothe low grade concentrate leaching 'andfelectifolytic circuit;

n 20.2Alc'opper extraction process compris-'-V 'i ing,l treatingjcopperfore tov 'separatea high"k grade andalow, gradeconcentrate, roasting f f' i the loW grade concentrate'to make aVK portion'.v

ofthe copperwater soluble and afportion acid soluble, vseparately roasting {the high grade@v concentrate, leachingv the -vroasted lorvjgra'dezl concentrate toiextract the Waterl soluble cop-y per as a relativelyfrich and `relatively pure;

copper solution, then "leaching the roasted y,lovr :grade concentrateto extract remaining acidsoluble copper as a.;relatively "impure, n, copper solutiomtreating the--relativelyrich l A fr andrelatively pure copper solutiontwith thei" roastedihgh grade Copper concentrate and 'electrolyzillg thersolution to' deposit. the @Qpper, and separately'precipitating the copper from the relatively impure copper solution.,

,2L A pro/cess Comprising-,treating Copper ore to separate a high 'grade and a low grade,

copper concentrate, roasting the4 high` grade concentrate, leaching the'roasted hig'hrgrade concentrate to extract a lpoi-"tion ,of theeopper,

. I electrolyzing the resulting copper vsolution in one electrolytic circuit, mixing the partly concentrate, leaching'the. high grade concentratel tovk extract the copper,Vv electrolyzing the resulting relatively pure and relatively richcopperl solution to deposit the`v copperanl 136;.-

o generate acid, leaching the roasted lowgrade;

concentrate with the regenerated; acid solution to, extract the copper, separately-electrolyzgiiigr Y the resulting relativelyimpure copper solu 7^ tion. to deposit the copperV and regenerate:

acid, and appl-ying the resulting relatiyely impure regenerated acid solution tothe I niiredY oxide and sulphide copper; oreto diSSQlgYe the;

vcopper therefrom iniV its oxidized Combinations. Y 4

123. A process comprising, leacllllgrCopper` ore to,l extract the copper, precipitating soliueA ble-,ironI from a portion of the copper s0. ution,

Y electroliyzing the solutonlow njsalts ofron.

to;y deposit the copper and regenerate acid', re,-A dissolving the precipitated iron with the 118:

' generated acid; solution thusg-ivinga: copper solution high inV saltsoiron, and separately;

electroliyzng the copperxsolution high; in salts of iron. Y l

24;; A process Comprising, leaching; copperore to extract a'portion of thegcopper as.

Y a, copper solution'relat'ively low-v all' Salts ot ironl then; leaching the ore to extract: another portion asa copper solution relativelyk high.4

in salts.- of iron,` and separately electrolyzing; the soliutions'to deposit the copper; Y v 2f5. A process comprising, treating copper ore to obtain aportion of the copper` asfaf relatively pure copper solution and another portion asa relatively impure-'copper solo?. -v

tion containing'sa-ltsof' iron, electrolyz-ingthepure copper solution-sto. deposit the copper and regenerate acid: in onev electroliyticcir.A f

cuit, and electrolyzing theimpurecopper so: lutionY containing salts of iron in another electnolyticI circuit to depositfthecopper and regenerateierrc non,y applying concentrated @Opp-e1? sulphide to the electrolyzecl impurecoppe'rsolution to reduce the ferrie iron, and againeleetrolyzing4 the solution.

. 26. A process comprising, treating copper bearing material to obtain a portion of they copper l'as a copper solution low in soluble iron andanother por-tion asa copper solution high in soluble iron, e-lectrolyzing the. copper-Solution low insoluble iron to precipitate the copper, and separately:'precipitating the copper from the solution high in soluble iron by alternately subjecting the solution to reduction and electrolysis.V

22. Al process comprising, treating copper bearinginaterial to obtain a portion of the copper-v asJ a copperY solution 10Wv in soluble irQIfl' and another portion as a copper solutionk high in soluble iron, electroly'zing the copper solution lo-W insoluble iron to precipixtate the copper, and separately precipitating the copper from thesolution` high inv soluble iron, by lalternately subjecting the solution-y to: reduction and to, electrolysis with insoluble anodes. l s s .WILLIAM E. GREENAWTALT.,

iso 

